In the conventional electrical water heaters and heat-pump hot-water feeders, hot water stored in a storage tank is typically produced at night when the power demand is low and used during the daytime. As a result, the operation of appliances is shifted to the nighttime when the power demand is lower than during the daytime, thereby making it possible to level the power load. Further, the electricity cost can be reduced for the user by using electricity in the nighttime when the electricity rate is low.
Further, the time-zone-depending electricity rate system is presently used in which the electricity rate differs for each preset time zone. In the future, the environment relating to power usage, such a wide spread of solar cells, installation of storage batteries, and development of new household electrical units will change significantly, and real time pricing (RTP) in which the electricity rate changes in real time will be introduced.
A system in which, in addition to the conventional nighttime use of electrical water heaters and heat-pump hot-water feeders, household electrical appliances such as refrigerators, washing machines, and rice cookers are connected via a network to a server and load leveling and power rate reduction are performed by changing the usage time zone of the household electrical appliances with the server has been suggested as a method for additional load leveling and power rate reduction to meet the demands of such new environment (see, for example, Patent Literature 1). In the system described in Patent Literature 1, the user inputs the desired usage time of household electrical appliances by operating an input operation panel. Further, a configuration is disclosed in which at the server side connected to the household electrical appliances, an optimum usage time zone plan is created with consideration for the usage time desired by the user and characteristics of the household electrical appliances that are to be used, and the household electrical appliances are controlled according to this plan.
However, in the above-described conventional technique, although the algorithm for shifting the operation time interval of household electrical appliances to the optimum time zone with consideration for the electricity rate or the like is described, how to use the time shift functions of household electrical appliances is not sufficiently investigated.
The advantage of using the time shift function by operating the input operation panel installed at the household electrical appliances and used in the conventional manner is that the traditional operation method can be employed and intuitive input/operations are performed. However, the conventional input operation panels installed at the household electrical appliances have not been designed under an assumption of displaying information relating to a time shift. Therefore, when the conventional input operation panel is used as is, limitations and restrictions are placed on the display contents and the entire information relating to a time shift cannot be sufficiently displayed. The resultant demerit is a lack of convenience for the user using the time shift function.